chapter 11: cell signaling II

Question 1

what are the components of a signal transduction pathway?

Answer 1

• the signal (ligand)
• a receptor of the signal: protein
• response to signal

Question 2

what are the steps of signal transduction?

Answer 2

1. reception
2. transduction
3. response

Question 3

signal reception

Answer 3

the signal (ligand) binds to the receptor of the signal

Question 4

how is the response to the signal created after the ligand binds to the receptor?

Answer 4

the receptor changes shape

Question 5

is the ligand changed after binding?

Answer 5

no

Question 6

is the receptor always active?

Answer 6

no, it alternates between active and inactive conformations

Question 7

is the binding of the ligand to receptor reversible?

Answer 7

yes

Question 8

are receptor proteins highly specific for their ligands?

Answer 8

yes

Question 9

what type of receptor do polar/large signals have?

Answer 9

transmembrane protein: a receptor that is embedded in the membrane because the signal cannot diffuse through the cell membrane on its own

Question 10

what type of receptor do nonpolar signals have?

Answer 10

an intracellular receptor that is in the cytosol or nucleus because nonpolar signals can diffuse directly across the lipid bilayer of the cell membrane

Question 11

what happens after ligand binding causes the receptor to change shape?

Answer 11

reveals NLS tag to enter nucleus where it affects protein making
- receptor is considered the transducer and effector

Question 12

are all receptors are transducers and effectors?

Answer 12

no, it usually does not produce the effect

Question 13

what happens when the receptor does not act as an effector?

Answer 13

after the receptor binds to the ligand, it starts a chain of signaling that eventually creates a response

Question 14

two types of receptors that start a chain of signaling

Answer 14

1. G-Protein Coupled Receptors
2. Receptor Tyrosine Kinases

Question 15

G-Protein Coupled Receptors

Answer 15

the receptor that binds to the signal, which gets binded to GTP to activate the G-protein

Question 16

GTP

Answer 16

nucleotide important for cell signaling

Question 17

GEF

Answer 17

GDP/GTP exchange

Question 18

GAP

Answer 18

GTP hydrolysis

Question 19

steps of G-Protein Coupled Receptors

Answer 19

1. signal enters the GPCR
2. inactive form of G protein has GDP bound
3. activation of G protein by binding with receptor and exchange of GDP for GTP
4. activated G-protein moves through cell membrane and binds/activates next protein

Question 20

Receptor Tyrosine Kinases

Answer 20

enzyme-linked cell-surface receptors that phosphorylate themselves after binding a signaling molecule

Question 21

protein kinase

Answer 21

adds a phosphate group to proteins and causes enzyme to change shape and open active site, which allows the substrate to bind to it

Question 22

phosphatases

Answer 22

removes phosphate groups from proteins

Question 23

steps of receptor tyrosine kinases

Answer 23

1. kinases add phosphate to change shape of proteins
2. shape change can reveal binding site so protein can phosphorylate/activate the next protein in the signaling pathway

Question 24

signal transduction

Answer 24

a series of molecular switches turn each other on by changing next molecule in pathway

Question 25

are more than one responder or transducing protein may be involved?

Answer 25

YES

Question 26

can more than one second messenger relay the signal from the receptor in the membrane to other regions in the cell?

Answer 26

yes and they can also amplify the signal

Question 27

kinase cascades

Answer 27

add/remove phosphates using kinase and phosphatase

Question 28

what activates a kinase?

Answer 28

Ras triggers its phosphorylation

Question 29

what does the active kinase start?

Answer 29

phosphorylation cascade

Question 30

phosphorylation cascade

Answer 30

each kinase phosphorylates a different kinase until a response is triggered in the cell

Question 31

why is signaling amplified?

Answer 31

1. larger cellular response 2. more molecules impacted 3. multiple response can be made simultaneously

Question 32

what are two kinds of second messengers?

Answer 32

cAMP and DAG + IP3

Question 33

cAMP

Answer 33

adenylyl cyclase gets activated to transform ATP into cAMP

Question 34

what is adenylyl cyclase?

Answer 34

a membrane protein

Question 35

steps of cAMP activation

Answer 35

1. GPCR binds ligand. GEF exchange GDP for GTP on G-protein 2. activated G-protein migrates to adenylyl cyclase and turns it on creating cAMP 2nd messengers 3. cAMP binds to channel protein, opening and allowing ions to travel down their concentration gradient

Question 36

fight or flight response using adenylyl cyclase

Answer 36

1. epinephrine (signal and 1st messenger) 2. cAMP (second messenger) 3. activates glycogen phosphorylase to release glucose allowing it to help create a fight or flight response

Question 37

PIP2

Answer 37

DAG + IP3

Question 38

what does phospholipase C do when activated?

Answer 38

cleaves PIP2, releasing the secondary messengers IP3 and DAG

Question 39

what do IP3 and DAG do?

Answer 39

activate different cellular responses

Question 40

what can dag initiate?

Answer 40

exocytosis

Question 41

what can IP3 initiate?

Answer 41

release of Ca2+ ions from smooth ER

Question 42

signal response

Answer 42

cells respond to signals by activating enzymes, opening membrane channels or initiating gene expression

Question 43

what does cell response depend on?

Answer 43

signal and cell type

Question 44

what kind of responses do second messengers produce?

Answer 44

slow and fast responses

Question 45

what do complex multi-component signal transduction pathways provide?

Answer 45

1. opportunities for feedback 2. signal amplification 3. interactions inside one cell between multiple signals and signaling pathways

Question 46

what two ways can signals activate?

Answer 46

1. active when phosphorylated by both pathways 2. active when phosphorylated by either pathway

Question 47

are enzymes always active?

Answer 47

no, cells regulate the activity of transducer molecules to respond to signal and then return to inactive state